Phonograph turntable control system

ABSTRACT

When the user presses a touch-activated switch a first time, a first digital storage device becomes set and furnishes a platter-motor-start signal to the control electronics of the platter drive motor. If the touch-activated switch is pressed a second time, the first digital storage device becomes reset, and the signal commanding that the platter drive motor operate terminates. A second digital storage device likewise assumes its set and reset states in response to the first and second pressing of the touch-activated switch. Sensors ascertain various operating conditions during the course of turntable operation, such as the swinging of the tone arm to the position corresponding to the lead-in groove of a phonograph record. The states of the digital storage devices are additionally dependent upon the conditions sensed by the sensors. Logic circuitry interprets the combinations of states of the digital storage devices and causes the requisite turntable operations to be performed, e.g., lifting and lowering of the tone arm, inward and outward swinging of the tone arm, initiation and termination of rotation of the platter, audio muting, and the like.

This is a continuation of application Ser. No. 835,535, filed Sept. 22,1977, now U.S. Pat. No. 4,132,935.

BACKGROUND OF THE INVENTION

The invention concerns a phonograph turntable control system, providedwith means for lifting and lowering the tone arm, means for swinging thetone arm horizontally, means for detecting when the tone arm has beenlowered onto a record and when the tone arm has reached the end of arecord, and provided with touch-activated switches or touch buttonsactivated by the user, with settable and resettable electrical orelectronic storage devices which register commands for the swinging,lifting and lowering of the tone arm and for turning on and off thedrive motor for the platter.

In conventional phonographs, the control functions for the platter motorand the tone arm are implemented using predominantly mechanical means.Use is typically made of transmissions, gearing, levers, and the like.However, mechanical components such as these wear and age quite rapidlyand are very susceptible to malfunction.

For certain special functions, it has already been proposed to make useof nonmechanical control devices which make for a considerableimprovement in overall phonograph turntable construction. For example,German patent DT-PS No. 1,243,412 discloses a shutoff system for theplatter drive motor of a phonograph turntable. The tone arm hasconnected to it a light shield which, when the tone arm swings, movesthrough the light path of a photoelectric detector. The speed ofswinging movement of the tone arm is sensed, and when a certain speed ofswinging movement is reached, the platter drive motor is shut off bymeans of a transistor-controlled switching relay. An RC-circuit receivesthe output signal of the photodetector and produces a voltage whosemagnitude is dependent upon the rate of change of the light-dependentcurrent produced by the photodetector.

German published patent application DT-OS No. 1,810,983 disclosesanother photoelectric switching system for phonograph turntables. Thephotoelectric switching system includes a stationary light source and astationary light detector. A deflecting mirror is mechanically coupledto the tone arm and moves as the tone arm becomes inwardly displacedduring tracking of the spiral record groove. The deflecting mirror ispreferably oriented perpendicular to a radial plane which passes throughthe swinging axis of the tone arm. When the tone arm reaches a positioncalling for the initiation of a switching operation, the deflectingmirror directs the light from the light source onto the light detector.

Other automatic switching devices are known in the art, for switchingoff a phonograph at the end of a record, for lowering the tone arm andfor controlling the tone-arm drive mechanism, for example in Germanpublished patent applications DT-OS No. 19 57 562, DT-OS No. 20 54 880,DT-OS No. 20 11 005 and DT-OS No. 19 54 673, and also in German allowedpatent application DT-AS No. 19 17 241. However, these various automaticswitching systems relate to various individual aspects of electronicphonographic control.

The Audiodynamics Corporation (ADC Accutrac 4000, brochure AVO 17608)produces an automatic phonograph turntable in which various functionscan be triggered by pushbutton action or by wireless remote control.However, this known system is not provided with sensor operator controlelements.

Finally, German published patent application DT-OS No. 21 04 692discloses a system in which the various functions to be performed forturntable control are made to have a much more automatic character, andare implemented using electronic means. The tone arm is moved by twoelectromechanical positioning devices, one for horizontal swinging ofthe tone arm, the other for vertical lifting and lowering of the tonearm. Use is made of two electrical storage devices for storage ofswing-in and swing-out information. The tone arm is lifted as soon asone of the storage devices registers a signal. Swinging of the tone armis not possible until after the lifting movement of the tone arm hasbeen completed. The storage devices are erased when tone-arm-positiontransducers signal the end of the operation involved. The use ofsettable storage devices makes it possible to dispense with the use ofelectrical switches of the type which must be held locked in activatedposition by mechanical locking means; instead, use can be made oftouch-activated switches, very-low-force touch buttons, and the like.

The present invention proceeds from the state of the prior art lastreferred to.

SUMMARY OF THE INVENTION

It is a general object of the invention to provide a turntable controlsystem which uses electronic components to control the lifting, loweringand swinging of the tone arm, and in which manual initiation ofautomatic operations can be performed using simple touch-activatedswitches, momentary switches activated by very-light-pressuretouch-button action, and the like, so that manual initiation ofautomatic operations can be performed with very great ease and using aminimum of manual force.

These objects can be met, in the preferred embodiment of the invention,using first and second electronic digital storage devices. When the userpresses a touch-activated switch a first time, the first digital storagedevice becomes set and furnishes a platter-motor-start signal to thecontrol electronics of the platter drive motor. If the touch-activatedswitch is pressed a second time, the first digital storage devicebecomes reset, and the signal commanding that the platter drive motoroperate terminates. A second digital storage device likewise assumes itsset and reset states in response to the first and second pressing of thetouch-activated switch. Sensors ascertain various operating conditionsduring the course of turntable operation, such as the swinging of thetone arm to the position corresponding to the lead-in groove of aphonograph record, etc. The states of the digital storage devices areadditionally dependent upon the conditions sensed by the sensors. Logiccircuitry interprets the combinations of states of the digital storagedevices and causes the requisite turntable operations to be performed,e.g., lifting and lowering of the tone arm, inward and outward swingingof the tone arm, initiation and termination of rotation of the platter,audio muting, and the like.

With the inventive system, incorrect manual initiation of automaticallyperformed operations becomes almost impossible. Also, with the inventiveconcepts, it becomes possible to combine an automatic touch system witha searching function.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a first embodiment of theinvention;

FIG. 2 is a schematic block diagram of a portion of a modified secondembodiment, depicting only that part of the second embodiment whichdiffers from the embodiment of FIG. 1;

FIGS. 3a to 3c together form the circuit diagram of an exemplary circuitfor the embodiment of FIG. 1; and

FIGS. 4a and 4b depict mechanical aspects of the swing unit and the liftunit for the tone arm of the turntable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary turntable depicted in FIG. 1 comprises a tone-arm swingunit 1 driven by a control amplifier 4 over a switch 3; a control systemfor providing appropriate signals to said amplifier 4; a lift device 2for raising the tone arm or allowing it to drop; a drive system 15 forthe platter, comprised of a motor and associated electronics of such anature that starting and stopping of the motor, and the speed of themotor, may be controlled by purely electrical means; and certainsubsystems, namely means for detecting the position of the tone arm andproducing a certain electrical signal corresponding thereto, shown as 22in FIG. 1; means for sensing overcurrent conditions in the drive coil of1, which overcurrent sensor is denoted by 9a and 9b; means forcontrolling the raising and lowering of the tone arm and its angularposition in response to a manual control device 19; means for providingelectrically a suitable anti-skating compensation force, and means formuting the audio output at desired times, generally at all times exceptfor the normal playing mode, these being encompassed by a subsystem 21,in combination with a muting device 30.

The control circuit includes two bistable storage devices, hereafterreferred to as flip-flops, but which are not restricted to the meanscustomarily associated with the designation "flip-flop." The operationof the turntable is related to the state of said flip-flops, which statemay be established or changed in response to external commandsintroduced by the user, and/or by certain signals generated internallyby subsections of the turntable. Each flip-flop consists of an output,designated Q; an input designated S which causes the output to assume anactive or logically high condition; and a plurality of inputs designatedR which singly or in combination cause the output to assume an inactiveor logically low state.

The outputs of the two flip-flops 8, 12 may together represent a maximumof four distinct and distinguishable states. These distinct states, orsome of them, are used to control the operation of the turntable by asuitable arrangement of logic elements connecting said flip-flops to theseveral parts of the turntable mechanism. A means is provided whereby acertain desired state of the outputs of the flip-flops exists followingthe application of supply voltage to the circuitry but prior to theentrance by the user of any operative commands.

Provision is made for the user to initiate commands to the controlsystem for purposes of automatic operation, which are of two kinds. Thefirst is the START command, which initiates the playing of a record. Thesecond is the STOP command which discontinues the playing of a recordand returns the tone arm to its rest and stops platter rotation. Thesecommands may be introduced by a variety of means, including but notnecessarily limited to, the use of pushbuttons or other switching means;in general, any means which is capable of producing suitable voltagepulses at the appropriate flip-flop inputs and which are designatedsymbolically in FIG. 1 by switches 14 and 13 for START and STOPrespectively. Such commands may also be introduced in conjunction withelectronic control of platter rotational speed as will be discussed inconnection with FIG. 2. Furthermore, such START and STOP signals may beproduced by the repeated actuation of one button by the provision of atoggling or alternate-action means.

The START signal is introduced into the S input of first flip-flop 12,and into the S input of a second flip-flop 8, which in each case resultsin the output of the respective flip-flop assuming an active or highstate. The STOP signal is introduced into one R input of first flip-flop12, and also into one R input of second flip-flop 8, causing the outputsof both flip-flops to assume an inactive or low state. Thus, START andSTOP signals result in distinct output states of flip-flops 12 and 8.Additional distinct states of such flip-flop outputs result fromintroducing certain reset signals in a particular manner as will bedescribed.

The turntable is required to perform at least the following distinctoperating functions: (1) a START function, in which the tone arm islifted and caused to swing inward until a certain desired radialposition over the platter is reached, which position corresponds to thelead-in groove of the record and which may if desired be made selectableby the user to accommodate various record diameters. During this STARTfunction the platter may be caused to rotate. A second function (2) is aplaying function in which the arm is lowered, and the platter is causedto rotate. A third function (3) is the STOP function in which platterrotation ceases, the arm is lifted and caused to swing outward. SuchSTOP function may be selected by the user by means of 13 or a subsystemperforming the function of switch 13; or, alternatively, the STOPfunction may be initiated by the sensing of the arm position in such amanner as to indicate when the arm has reached the run-out groove areaof the record, which position may be made selectable by the user toaccommodate various record diameters. A fourth "stand-by" function isprovided in which outward movement of the arm ceases and the arm isallowed to sink downward, the platter remaining stationary.

Certain desirable additional functions are accomplished in connectionwith the four conditions enumerated above. These are (1) an audio mutingfunction, and (2) an anti-skating compensation function. The audiomuting function is so arranged that no audio output results from theturntable during START, STOP, and "stand-by" operating modes; andfurthermore, that at the beginning of playing mode operation a timedelay is provided to avoid the transmission of stylus set-down noise tothe reproducing system. An electronic anti-skating compensation means isprovided whereby a constant current of magnitude and polarity such as tocause swing unit 1 to develop a rotational force to oppose the skatingforce developed during the playing of a record is supplied to swing unitdrive coil 125 (shown in FIG. 2). This current may be adjusted inmagnitude by control 245 (discussed later with respect to FIG. 3) whichis accessible to the user, resulting in an anti-skating force suited toparticular circumstances of use. Such anti-skating compensation isapplied only during play mode, and is subject to time delay at thebeginning of play mode to preclude such compensating force from movingthe arm angularly and thereby failing to set down at the desiredlocation on the record.

The manner in which these operating mode functions are performed willnow be described. A START command causes the respective outputs offlip-flops 12, 8 to become high. This condition is decoded, for exampleby the use of NOR-gate 145 in FIG. 1, such that a signal 6 is applied toan input of drive amplifier 4 and also to an input of OR-gate 20. Theoutput of OR-gate 20 causes arm lift 2 to be energized and the arm tolift, which lifting also closes switch 3, switch 3 being mechanicallycoupled to the arm lift mechanism, whereby drive coil 125 (shown in FIG.3) of swing unit 1 is connected to amplifier 4. The input to whichsignal 6 is applied is such as to cause a resulting inward angularmotion of the tone arm. NOR-gate 145 is provided with a high signal fromflip-flop 12 causing the output of gate 145 to be low, and consequentlysignal 5 is zero.

Upon reaching a preselected point, position sensor subsystem 22 deliversan output signal which is transmitted through gate 33 and time delay141, 142, 143, 144 (shown in detail in FIG. 3) to one reset input offlip-flop 8. By this means, flip-flop 8 is caused to reset and itsoutput becomes low. Signal 6 therefore becomes zero and arm motionceases since amplifier 4 receives no input signals. The low state offlip-flop 8 also removes the activating signal from lift 2 which hasbeen transmitted through OR-gate 20. The arm is thereby lowered onto therecord. The completion of this process results in the attainment ofnormal playing mode operation. During normal playing mode, there remainsan output signal from position sensor 22. Removal of a signal from lift2, as just described, also removes a signal from the muting andanti-skating sybsystem 21. The removal of such signals results, after atime delay, in the actuation of means to permit transmission of theaudio signal of an anti-skating compensation current, after the timedelay has elapsed, to the drive coil of swing unit 1.

When the arm has attained the position corresponding to the lead-outgroove of the record, the signal from position sensor 22 becomes zero.The output of flip-flop 8 has been made zero previously as describedabove. Consequently, zero output from position sensor 22 is communicatedto NOR-gate 18 via transmission gate 33. The output of NOR-gate 18 isthen caused to be high, which high state output is applied to one resetinput of flip-flop 12, causing the output state of this flip-flop tobecome low. The respective outputs of the two flip-flops 12 and 8 arenow low. The output of outward current sensor 9a is also low, and theapplication of low state signals to every input of NOR-gate 145 causesits output to become high. This output is applied as signal 5 toamplifier 4 and also to one input of OR-gate 20. The input of amplifier4 to which signal 5 is applied is such as to result in outward motion ofthe tone arm. The presence of a high signal at one input of OR-gate 20causes the lift 2 to be activated as previously described. The arm isthen lifted, upon completion of which switch 3 is closed, and a drivesignal from amplifier 4 is applied to drive coil 125 of swing unit 1such as to move the arm outward. This state of the circuit correspondsto stop mode. The STOP mode may also be caused to exist by the user atany time during normal playing mode operation by the user causing a STOPcommand to be introduced via switch 13 or an equivalent means. Such acommand is communicated to one reset input of flip-flop 12, and also toone reset input of flip-flop 8. This causes the respective outputs ofboth flip-flops to become low and the stop function procedure previouslydescribed takes place.

The function of delay circuit 141, 142, 143, 144 is to prevent animproper sequence of flip-flop reset operations, by preventing thetransmission of a signal to one reset input of flip-flop 8, untilNOR-gate 18 has assumed a steady-state condition of low state outputresulting from the presence of one or more high state inputs to NOR-gate18. The function of transmission gate 33 will be explained below.

An overcurrent sensor subsystem 9 is also provided, consisting ofoutward current sense circuit 9a and inward current sense circuit 9b,the designation "outward" and "inward" corresponding to the polarity ofcurrent through the drive coil 125 and/or the voltage existing at theoutput of amplifier 4 under conditions of outward and inward armmovement respectively. The overcurrent sensors detect and respond to theelevated currents and/or the corresponding elevated voltage drops whichobtain when motion of the arm is mechanically hindered and one or theother inputs of amplifier 4 is supplied with a high state signal. Theoutward overcurrent sensor 9a is of such a nature that if the input tothe overcurrent sensor 9a exceeds a predetermined threshold value for acertain length of time, the output of sensor circuit 9a will assume ahigh state, and will furthermore remain in such high state until itsreset input is activated. Such an overcurrent sensor as described may beimplemented by means of a suitable threshold-responsive circuit,followed by an integrator, followed by a suitable bistable storagedevice such as a flip-flop or other resettable bistable storage. Analternate arrangement could consist of an integrator, followed by athreshold detector, followed by the aforementioned suitable bistablestorage device. A third possible arrangement might utilize an integratorfollowed by a bistable storage device of such a nature that a thresholdeffect is inherently present in the set input of such storage device.

At the completion of play of a record, or following the initiation bythe user of the STOP function, the state of the circuit is as previouslydescribed as STOP mode. In such a case, the arm will be subject to anoutward-going force from swing unit 1 for an indefinite time. Amechanical stop or other hinderance is, however, provided in such a waythat the motion of the arm is mechanically hindered from further outwardmotion when the arm is located over the arm rest. The overcurrentsituation thereby existing due to such hinderance will be sensed byoutward current sensor 9a, and the output of sensor 9a will become highafter a period of time. The high output of current sensor 9a is appliedto one input of NOR-gate 145, causing the output of NOR-gate 145 tobecome low. The output of NOR-gate 145 corresponds to the signal 6,which consequently becomes zero. In this case, no signals are applied toamplifier 4 and rotational force ceases to be applied to the arm viaswing unit 1. Also, the signal applied from the output of NOR-gate 145to one input of OR-gate 20 is zero, and the output of OR-gate 20 becomeslow, removing the lift signal from lift 2, thereby causing the arm todrop. This state of the circuit corresponds to the "stand-by" condition.

The outward current sensor 9a has also a rest input which is connectedto the junction of the START switch 14 or its equivalent, the set inputof flip-flop 12, and the set input of flip-flop 8. By this means, theoutput of current sensor 9a is caused to be in a low state whenever aSTART command is introduced into the turntable. Furthermore, thebistable storage element contained in 9a as previously described, is soarranged that the output of such storage device is low following theapplication of supply power to the circuitry.

Should the arm be mechanically hindered at any time during a conditionof outward motion, the series of events previously described will takeplace and the stand-by condition will obtain. By this means, possibledamage to the arm and/or parts of the control system is avoided.

In an analogous manner, hinderance of the motion of the arm underconditions of inward motion will cause the output of the inward currentsensor to become high. The inward current sensor consists of anintegrator and a following threshold circuit. Alternately, a thresholdcircuit followed by an integrator could be employed. Also, the functionof threshold detection could be performed by subsequent circuitry ifsuch subsequent circuitry exhibits a suitable threshold characteristicin its operation. The existence of a high state of the inward currentsensor 9b output, which output is connected to one reset input offlip-flop 8, causes flip-flop 8 to be reset. One input of NOR-gate 18 isconnected to the output of flip-flop 8. Inward motion condition existsonly when the arm is located between the arm rest and the beginning of arecord; therefore, the output of position sensor 22 is low. This lowstate is transmitted through transmission gate 33 to the other input ofNOR-gate 18, causing the output of NOR-gate 18 to become high. This highsignal is transmitted to one reset input of flip-flop 12, thus resettingsaid flip-flop. Both flip-flops are now reset, constituting the STOPcondition.

It is desirable that the rotation of the platter be automaticallycontrolled. This is accomplished by connecting the output of flip-flop12 to the platter electronics 15. The output of flip-flop 12 is highonly under conditions of (1) START and (2) normal playing condition. Asuitable circuit means is provided in platter electronics 15 such that ahigh state signal at said input causes the platter drive motor to beactivated, and the motor not to be activated under conditions of lowstate input. The rotational speed of the motor may further be madesubject to control by the user, and in addition such speed control maybe accomplished in combination with a START command as described inconnection with FIG. 2.

A manual cueing means is provided whereby the arm can be caused to lift,or to lift and swing, under the control of the user without the need forphysical contact with the arm by the user. Such a cueing device 19consists of sensor contacts 160, hereafter referred to as "lift sensor",and a means for causing a control signal of variable magnitude andpolarity to be obtained in response to the position of a button or otherdevice in conjunction with a potentiometer.

Actuation of lift sensor 160 causes a high logic state to exist, whichis communicated to OR-gate 20, transmission gate 33, and muting andanti-skating subsystem 21. Transmission gate 33 is of such a nature thatthe application of a suitable gating signal inhibits the passage of asignal through the circuit. Such gating signal corresponds to said highstate signal from lift sensor 160. Thus, when the manual lift functionis activated by means of lift sensor 160, transmission of signals fromposition sensor 22 to the remainder of the circuit is prevented, wherebythe user is enabled to move the arm at will without causing any changein the state of the control flip-flops 12 and 8 which might otherwiseoccur due to the action of position sensor 22. Additionally, a highsignal from 19 is applied to OR-gate 20 when lift sensor 160 isactivated, resulting in a high output from OR-gate 20 and activation oflift 2. A high state signal resulting from the activation of lift sensor160 is also applied to one input of muting and anti-skating circuit 21.Such input causes the immediate cessation of audio output from theturntable and also the immediate cessation of anti-skating currentapplied to drive coil 125.

The signal from control 23 is applied to amplifier 4 in such a manner asto control the drive signal to coil 125 through switch 3, indicatedsymbolically in FIG. 1 by a summation at one input of amplifier 4. Thepotentiometer 23 is so connected that either positive or negativevoltage may be obtained in order that the tone arm may be moved ineither an inward or an outward direction; and the magnitude of suchvoltage may be varied by the user to control arm rotation velocity.

An extension of the basic system is shown in FIG. 2. FIG. 2 representsessentially only those elements which differ from FIG. 1. In thisextension, automatic fully electrical control is extended to platterrotational speed selection and integrates speed selection and START andSTOP command functions. The STOP function is supplied by suitable meanssuch as an electronic sensor, responding to skin resistance of thefingertip, or other suitable excitation, which means replaces the switch13 in FIG. 1. Two additional densors 25 and 26 are provided, whichsensors operate in a manner similar to the sensor associated with theSTOP function as just described. An OR-gate with one input connected tosensor 25 and one input connected to sensor 26 at its output a signalwhich replaces switch 14 in FIG. 1. By this means, actuating eithersensor 25 or sensor 26 initiates a START command in the mannerpreviously explained. Sensors 25 and 26 are also connected to one inputand another input respectively of a bistable storage device 24. Thisdevice, which may be an electronic flip-flop circuit or othernon-mechanical device, has two outputs. One output exhibits a high statewhen the corresponding input connected to sensor 25 is activated, andthe other output exhibits a high state when sensor 26 is activated. Inboth cases, the logic state is retained at the output of 24 afteractuation of either sensor 25 or sensor 26 has ceased. The purpose ofthese two outputs of flip-flop 24 is to provide information to otherportions of the turntable regarding (1) desired platter speed, forinstance 331/3 or 45 rpm; and (2) an associated record diameter, such as12 inches and 7 inches. Each output of flip-flop 24 is connected to acorresponding input of motor electronics sybsystem 15, one input causingthe motor to revolve at one desired speed when the motor is energized,and the other such input causing the motor to revolve at some otherdesired speed when the motor is energized. The two outputs of flip-flop24 are also connected to each of two inputs of arm position sensor 22.Said inputs are so arranged that the activation of one causes onephotodetector, corresponding to a certain record diameter, to be active.Likewise, an activation of the other of the said inputs causes anotherphotodetector corresponding to another record diameter to be active. Bythese means, a further improvement is offered to the user in that STARTand the selection of platter speed and record diameter are performed inone and the same act of the user.

The description of the several means whereby START and STOP commands maybe entered into the turntable control system is not intended to excludeother possible means. In particular, means providing alternate ortoggling action associated with a single knob or button or rocker orother actuator accessible to the user may be used. By this means, afirst actuation would cause a START condition by setting flip-flops 12and 8, and a second actuation would cause a STOP command to beregistered by means of the resetting of both flip-flops 12 and 8. Suchalternate action may be provided for example by a suitable arrangementof switching contacts simultaneously actuated by a knob or button orrocker accessible to the user, which switches connect charge storageelements to the appropriate inputs of the said flip-flops, as depictedin FIG. 3. The use of other means of obtaining alternate action is notexcluded.

The swing unit 1 per se is a rotary electromagnetic device, for examplesuch as disclosed in FIG. 12 of German published patent applicationDT-OS 21 04 692. Inasmuch as the location of the lead-in groove of aphonograph record depends upon the size of the record, use is made of achangeover switch 16 which is coupled to the rpm selector 17 of thephonograph, in order to correlate the location of the lead-in groove ofthe record with its rpm and accordingly its diameter.

The manual control 19 is essentially comprised of a rotary, circular,touch-responsive knob, provided with a finger depression. If the userlays his finger into the finger depression of knob 19, this results inthe generation of a signal which commands that the tone arm be lifted.If the user turns the rotary knob 19, with his finger laid in the fingerdepression of the knob, in one rotary direction or the other, thisadjusts the setting of a cooperating potentiometer 23 and makes possiblemanual selection of the rate at which the lifted tone arm swings, i.e.,manually controlled cueing.

In the exemplary embodiment, lift unit 2 is a hot-wire device; i.e.,hot-wire lift unit 2 positively lifts the tone arm or permits the tonearm to lower, depending upon whether heating current flows through thehot wire of the lift unit 2 or not. As indicated by the broken lineextending from lift unit 2 to switch 3, the normally open switch 3 isclosed only when the lift unit 2 is holding the tone arm in liftedposition. Accordingly, unless the tone arm is in lifted position, swingunit 1 will not be energized and the tone arm will not swing in or out.

In FIG. 1, the touch-activated switches 13, 14 can be pure touchswitches which include no moving parts, for example of the type wherethe user's finger itself completes a current path, where the body heattransmitted from the user's finger causes the touch switch to generate asignal, and the like. Alternatively, the touch-activated switches 13, 14could be very-light-pressure momentary switches, e.g., pushbuttonswitches which are closed only so long as the user presses upon them;with the pressing force required to hold the switches closed beingextremely low, i.e., so that a very light touch upon them causes them tobecome briefly closed. If very-light-pressure momentary switches areemployed, then the two switches 13, 14 could, for example, be activatedby means of a single very-light-pressure rocker which the user wouldbriefly and lightly touch at one end to briefly close switch 14 and atits other end to briefly close switch 13.

FIGS. 3a to 3c together depict, in detail, a circuit diagram of anexemplary embodiment of the inventive tone-arm control system. Thiscircuit includes the swing unit 1, the lift unit 2, and the switch 3which connects the control amplifier 4 to the rotary electromagneticswing unit 1, all as discussed above in connection with FIG. 1. Theopening and closing of switch 3 is not performed electrically, butinstead by mechanical means; i.e., the mechanical state of tone-arm liftunit 2 controls the setting of switch 3. The control amplifier 4includes an operational amplifier 100 to whose output is connected anend amplifier stage comprised of transistors 101, 102, 103. Theresistors 104-108 and capacitors 109, 110 within control amplifier 4 arebiasing elements.

Flip-flop 12 is formed from two interconnected NOR-gates 137 and 138.Its normal output is connected to one input of gate 145. A complementoutput is also used, connected via resistor 185 to start/stop switch 14.The normal output of flip-flop 12 is also connected via resistor 153 toswitch 242. Both switches 14 and 242 are actuated simultaneously by thestart/stop button. When so activated, capacitor 141 is connected to onereset input of flip-flops 8 and 12, and capacitor 197 is connected tothe set inputs of flip-flops 8 and 12 and the reset input of the outwardcurrent sense 9a. In the non-actuated position, either capacitor 141 or197 will be charged to a logic high voltage level, the other to a logiclow level, depending on the state of flip-flop 12. When flip-flop 12 isset, the output is high and so capacitor 141 is charged and capacitor197 is not. Actuating start/stop causes the voltage on capacitor 141 tobe impressed on one reset input of each flip-flop 12 and 8, causing bothflip-flops to assume a low or reset state, corresponding to STOP. Whenflip-flop 12 is low or reset, the complement output of 12 will be high,charging capacitor 197 when switch 14 is in a non-actuated position.Actuating switch 14 and 242 supplies the voltage stored in capacitor 197to the set inputs of flip-flops 12 and 8 and the reset input ofovercurrent sensor 9a. In this way, alternate action of one start/stopknob is obtained.

Flip-flop 8 is composed of cross-connected NOR-gates 139 and 140.Resistor 151 insures that flip-flop 8 will assume a desired state,namely low or reset, during power-up. The output of flip-flop 8 isconnected to NOR-gate 145, resistor 146, one input of NOR-gate 18, oneinput of gate 157, and one input of OR-gate 20.

NOR-gates 141, 142, resistor 143, capacitor 144 constitute the delaycircuit mentioned above. Gate 141 has two inputs which stand in thelogical relationship of OR-gate to the output of gate 142. One input isconnected to the output of position sensor subsystem 33. Thiscorresponds to the circuit arrangement depicted in FIG. 1. Resistor 149and capacitor 148 form an integrating network for the inward overcurrentsensor 9b. As mentioned above, the threshold may be provided by thefollowing circuitry, which is the case here. The output of the inwardcurrent sense is shown in FIG. 1 as connected to one reset input offlip-flop 8. A logically equivalent connection is to make such aconnection via an OR function, which as just described is provided bygate 141 in combination with gate 142. This eliminates the requirementfor a fourth input in gate 140, which would otherwise exist.

The outward overcurrent sense 9a is provided by a threshold detectorconsisting of transistor 128 and resistors 132, 133, 131 and 129; anintegrator consisting of resistor 130 and capacitor 134; and a storagedevice comprised of NOR-gates 135 and 136 cross-connected as aflip-flop. Transistor 128 is biased by its associated resistors 129,132, 133 into conduction. When the input applied to 9a via resistor 131exceeds a predetermined negative voltage, transistor 128 ceases toconduct and the resulting positive voltage existing at the collector oftransistor 128 is applied via the aforementioned integrator to theaforementioned flip-flop. When the output of the integrator issufficient, the flip-flop will assume a set state. This constitutesdetection of an overcurrent condition in the outward-going mode. Resetof current sense 9a is provided via one input to gate 135. Resistor 248insures that this flip-flop assumes the desired set state followingpower-up.

Initialization of logic states following power-up is here accomplishedby resistors, since the CMOS logic elements used in the describedembodiment of the invention exhibit a high-impedance state a low supplyvoltage. Should other forms of logic elements be used to embody theinvention, it is understood that other forms of initialization may benecessary or desirable.

The OR-gate 20 is composed of resistors 164, 165, 166. The output ofOR-gate 20 is the point at which one terminal of each of said resistorsjoin and this output is connected to a lift driver circuit composed oftransistors 163 and 169 together with associated biasing resistors 167,168.

The muting and anti-skating subsystem 21 has three major subdivisions.The first is a time delay means 21a, which provides a small time delayfor signals increasing from zero, but which provides significant timedelay of a desired amount for signals decreasing from a high state levelto zero. The purpose is to provide, in conjunction with the remainder ofsybsystem 21, a means for providing delayed switch-on of audio signaltransmission means and anti-skating compensation means as discussedabove. Such a delay 21a is provided by diode 170, capacitor 112, andresistors 113 and 171.

The circuit 21 briefly mentioned with respect to FIG. 1 is here shownsubdivided into three stages: a time-delay stage 21a; an audio switch-onstage 21b; and an anti-skating stage 21c. Time-delay stage 21a comprisesa capacitor 112, a resistor 113, a diode 170 and a resistor 171.

The output of time-delay stage 21a is connected, via an OR-gatecomprising gate 111 and 114, to the audio muting sybsystem 21b. Mutingsystem 21b comprises a switching transistor 116, a relay winding 117, acapacitor 118, a resistor 119 and a diode 120. The emitter of transistor116 is connected to ground, whereas its base is connected to resistors115, 119 and to capacitor 118. The collector of transistor 116 isconnected to relay winding 117, to the right electrode of capacitor 118and to the cathode of diode 120. The audio switch controlled by muting21b is per se denoted by numeral 30, and is a double-pole relay switchcontrolled by relay winding 117. Switch 30, when closed, connects thesound pick-up system 31 of the phonograph to the connector 32 for theaudio amplifier of the phonograph.

An anti-skating compensation current is provided by a current sourceconsisting of transistor 121 and resistors 122 and 123. The magnitude ofcurrent provided by such a current source is determined by the voltageapplied to the base of transistor 121. This base voltage can be adjustedby the user by means of a knob connected to potentiometer 245.Potentiometer 245 is supplied with voltage from the aformentioned relayswitch circuit 21b via resistor 246. Consequently, the current source21c is active only under the condition that the relay coil 117,corresponding to allowed transmission of audio signals, is energized.

If the tone arm is swung outward and impacts against an obstacle, e.g.,an end stop, there flows through drive winding 125 an elevated current,also present at the output of control amplifier 4, and this elevatedcurrent is detected by current sensor 9a. In particular the basethreshold current of transistor 128 within current sensor 9a isexceeded, and transistor 128 changes its condition state. The resistors129, 130, 131, 132, 133 and the capacitor 134 serve to bias transistor128 and to establish a suitable threshold level for the transistor.

The overcurrent sensor 9a for outward swing also includes a flip-flopcomprised of two cross-coupled NOR-gates 135, 136.

The second input of NOR-gate 141 is connected to one input of theNOR-gate 18, the output of which is connected to platter-motor flip-flop12. Resistors 150, 151, 152, 153, 154 merely serve to properly bias thelogic elements. NOR-gate 18 has one of its inputs connected to theoutput of a photodetector logic circuit 33, which latter comprises threeNOR-gates 155, 156, 157, a diode 158 and a capacitor 159. The upperinput of NOR-gate 156 is connected to the output of a photodetector unit34 and to the upper terminal of a resistor 161 whose lower terminal isconnected to ground. The left input of NOR-gate 157 is connected to atouch-responsive element 160 of the manual control 19. Whentouch-responsive element 160 is touched by the finger of the user, thiscommands lifting of the tone arm. The manual control 19 furthermoreincludes the already discussed potentiometer 23. Additionally, the leftinput of gate 157 is connected to ground via a capacitor 162.

Transmission gate 33 is composed of two NOR-gates 155 and 156. Thesignal input is the upper input of gate 156 and the signal output is theoutput of gate 155. The gating input is the lower input of gate 156. Ahigh logic level at such gating input interrupts signal transmissionfrom signal input to signal output.

Gate 157 in conjunction with sensor 160 provides a high level outputwhen sensor 160 is activated. Diode 158 and capacitor 159 constitute apeak-hold circuit used as a noise removal filter to ensure properoperation of the lift function when a finger is applied to sensor 160.The output of this noise filter is connected to the aforementioned lowerinput of gate 156, and is also connected to one input of OR-gate 20. Theconnection shown for the right-hand input of gate 157 is not necessaryfor the proper operation of this circuit. The connection existingbetween the output of gate 156 and one input of gate 111 providesactivation of audio muting and cessation of anti-skating compensation bycircuits 21b and 21c when the manual lift sensor 160 is activated.

A signal commanding that the tone arm be lifted can be furnished fromthe cathode of the diode 158 in the photodetector logic circuit 33 tothe OR-gate 20. OR-gate 20 comprises a transistor 163 and four resistors164, 165, 166, 167. A command signal for tone-arm lift can also bereceived by OR-gate 20 from the output of NOR-gate 145 or from theoutput of swing-in flip-flop 8.

Connected to the output of OR-gate 20 is a lift switch 35 comprised of aresistor 168 and a transistor 169. The collecter of transistor 169 isconnected, via a diode 170 and a resistor 171, to the aforementionedtime-delay stage 21a.

The photodetector unit 34 includes a light shield 172 mechanicallycoupled to the tone-arm of the phonograph. Light shield 172 is guidedfor movement between a light source 173 and two photodetectors 174, 175.The two photodetectors are located behind respective ones of twoapertures in a light screen 176. The two photodetectors 174, 175 are solocated that the light shield 172 coupled to the phonograph tone armunblocks one photodetector when the tone arm has been swung to alocation corresponding to that of the lead-in groove of, for example, a33 rpm record, and unblocks the other photodetector when the tone armhas been swung to a location corresponding, for example, to the lead-ingroove of a 45 rpm record. The photodetectors 174, 175 are herephototransistors. The switches 16, 17 are selector switches forselecting different turntable speeds, e.g., the right switch 16, 17abeing for 33 rpm and the left switch 16, 17a for 45 rpm. The switches16, 17 are accordingly two-position switches, in the exemplaryembodiment.

The start and stop switches 13, 14 of FIG. 1 are likewise shown in FIG.3. These are used to start and stop the platter motor 176. Stopping ofthe platter motor 176 is effected through the intermediary of a motorstop switch 36.

FIG. 3 also depicts the internal circuitry of the platter-motor controlelectronics 15, e.g., including an integrated regulating block 177,resistors 178-186 and 190, potentiometers 187, 188, 189 and capacitors191-199, all serving to regulate motor speed. Preferably, motor speed isregulated in conventional manner using pulse-width modulation, thisbeing mainly performed by the integrated-circuit regulating block 177.

The control system furthermore includes a conventional power-supply unit37, comprising a transformer 202 and two rectifiers 203, 204, which canbe connected via a switch 205 to a wall outlet connector 206. Thecapacitors 207-215 and the fuse 216 perform conventional functions, andneed not be discussed in detail here.

The platter or structure carrying and turning with the platter isadvantageously provided with a flat, annular or disk-like magnetizablesurface provided with equiangularly spaced magnetized portions. Duringplatter rotation, the magnetized synchronizing portions are sensed by aninductive sensor 38, which latter generates an rpm feedback signal whichis applied to the platter-motor control electronics 15.

Two light-emitting diodes 250, 251 serve to indicate whether thephonograph is set for operation at 33 rpm or 45 rpm. To apply voltage tothese LED's 250, 251, these are connected in the current paths of aswitch 16, 17c which is coupled to the rpm selector switch 16, 17a.

FIGS. 4a and 4b depict certain mechanical details of the swing unit 1and the lift unit 2. The tone-arm mounting shaft is denoted by TS and isturned by the swing unit 1. The swing unit 1 includes two statorwindings 125, 126 which, as best seen in FIG. 4b, are of 90°configuration, as well as a rotor magnet 124, a lower flux-return ringof ferromagnetic material FR, and an upper flux-return ring at the topof the annular rotor magnet 124. Also shown in FIG. 4a is the hot wireHW of the lift unit 2 and the lift-unit-controlled switch 3, discussedearlier with respect to FIG. 1. Mounted on the tone-arm mounting shaftTS is the aforementioned light shield 172. Light shield 172 swingsthrough the light detector unit 34, between the light source 173 and thephototransistors 174, 175 thereof. The light detector unit 34 includesthe aforementioned apertured light screen 176, behind the apertures ofwhich the two phototransistors 174, 175 are located. The twophototransistors 174, 175 are located at different respective radialdistances from the axis of the tone-arm mounting shaft TS.

As best seen in FIG. 4b, the light shield 172 is provided with twoapertures, of different respective radial spacing from the axis of thetone-arm mounting shaft. The radially outer aperture, whose ends aredenoted by S1, S2, has a tangential angular span corresponding to theradial length of the modulated zone of, for example, a 33 rpm phonographrecord. The radially inner aperture, whose ends are denoted by S3, S4,has a tangential angular span corresponding to the radial length of themodulated zone of, for example, a 45 rpm phongraph record.

When the tone arm is swung inward, the light shield 172 coupled theretoturns clockwise (as viewed in FIG. 4b). During the inward swing, firstthe aperture edge S1 moves into the region of the phototransistors indetector unit 34; aperture edge S1 corresponds to the lead-in groove of,for example, a 33 rpm record. Next, aperture edge S3 moves into thephototransistor region; edge S3 corresponds to the lead-in groove of,for example, a 45 rpm record. Next, aperture edge S2 moves into thephototransistor region; aperture edge S2 corresponds to the end grooveof, for example, a 33 rpm record. Finally, aperture edge S4 moves intothe phototransistor region; edge S4 corresponds to the end groove of,for example, a 45 rpm record.

Returning to FIG. 1, the flip-flops 8, 12 and 24 can be, as shown inFIG. 3, electronic flip-flops of the type comprised of cross-coupledlogic elements, cross-coupled amplifier elements, or the like, and thisis preferred. However, in general, the devices 8, 12 and 24 could beelectrical storage devices of other non-mechanical types, e.g., magneticstorage cells, and the like. Also, whereas bistable (i.e., two-state)storage devices are herein disclosed for storage devices 8, 12 and 24,other storage devices having equivalent storage states, and thus capableof performing functionally equivalent command-signal storage, could alsobe used.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcircuits and constructions differing from the types described above.

While the invention has been illustrated and described as embodied in atwo-speed phonograph turntable control system, it is not intended to belimited to the details shown, since various modifications and structuralchanges may be made without departing in any way from the spirit of thepresent invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. An automatic turntable controlsystem for operating an electrical arm lifter that raises and lowers aplay arm upwardly and downwardly, for further operating an electric armrotator that pivots the play are inwardly and outwardly about the fixedpoint, and for still further operating an electric motor to turn it onand off, whereby such operation can be coordinated in accordance withuser instructions entered into the system by depression of electricalpushbutton switches and further in accordance with rotational positionof the play arm, comprising: an arm sensor cooperating with the play armgenerating an arm position signal which represents rotational positionof the play arm; a user-activated pushbutton-type on-off switch forturning the turntable on and off and causing the arm lifter, the armrotator and the motor to be appropriately operated after the on-offswitch is activated; a user-activated pushbutton-type switch, the armswitch cooperating with the arm lifter to raise and lower the arm whenthe turntable is turned on in accordance with operation of the switch;and an electrical control network cooperating with the arm sensor, thearm lifter, the arm rotator, the motor, the on-off switch and the switchto cause the play arm to be appropriately lifted, lowered and rotatedand to further cause the motor to be turned on and off in order to causea record to be played automatically and in order to further cause theplay arm to be raised and lowered during record play by activation ofthe cue switch.
 2. The system defined in claim 1, wherein the controlnetwork includes an anti-skate compensator which produces an anti-skatesignal, and wherein the arm rotator is responsive to the anti-skatesignal, the anti-skate compensator cooperating with the arm rotator in amanner that the play arm is urged outwardly during record play by thearm rotator to compensate for skating of the play arm during recordplay.
 3. The system defined in claim 2, wherein the anti-skatecompensator is variable and presettable by a user, and wherein theanti-skate signal is constant at a valve which corresponds to a settingto which the anti-skate compensator has been preset.
 4. The systemdefined by claim 1, further comprising a muting switch through which anaudio signal may be routed and which can permit and prevent such audiosignal from being transmitted through the muting switch, the mutingswitch cooperating with the control network in a manner that the mutingswitch will prevent an audio signal from being transmitted when the playarm is lifted and will further prevent an audio signal from beingtransmitted during a predetermined period of time, which period includesthe lowering of the play arm onto a record to be played, and the mutingswitch will permit an audio signal to be transmitted otherwise.
 5. Thesystems defined by claims 1, 2, 3, or 4, further including anobstruction sensor which detects any obstructions hindering movement ofthe play arm while the play arm is lifted and which cooperates with thecontrol network in order to turn the turntable off after such anobstruction is sensed.
 6. The system defined by claims 1, 2, 3, or 4,wherein the control network includes a speed selector for selectingspeed of operation of the motor.